1) Field of the Invention
The present invention relates to a method for diagnosing dry eyes, and more particularly to a method for diagnosing dry eyes by measuring corneal surface temperatures after one blinking and determining a rate of decrease in the corneal surface temperature due to the heat of vaporization in the tear evaporation of eyes of patients.
2) Related Art Statement
Dry eyes are a disease occurring as a disorder on the ocular surface, i.e. cornea and conjunctiva surfaces, due to qualitative or quantitative abnormality of tears. With the advent of the current information age office automation is now in rapid progress and consequently the video display terminal work is rapidly growing, resulting in increase in asthenopia or dry eye-complaining patients. It is said that Japan only has a latent dry eye patient population of eight millions. A primary cause of dry eyes has not been clarified yet, but the up-to-date knowledge suggests that the dry eyes are closely related to an abnormal autoimmunity or viruses.
Heretofore, diagnosis of dry eyes has been carried out not by a single test procedure, but by a combination of various test procedures. A particularly important test procedure for the diagnosis is an inquiry and most of asthonopia-complaining patients are diagnosed as suffering from dry eyes. Besides the inquiry, vital staining test and quantative determination of tears have been regarded as essential test procedures. In addition, other test procedures, such as quantitative determination of tear evaporation, have been also in practice.
The vital staining test is carried out by instilling a drop of physiological salt solution of rose bengal or fluoresecein into an eye as a reagent to observe the resulting staining state and measure a tear break-up time (BUT) at the same time Toda et al: Atarashii Ganka (New Ophthalmology), 8 (7), 1021-1027 (1991)!. The procedure for quantative determination of tears includes a Shirmer's test and a cotton thread test According to the Shirmer's test, a strip of filter paper is attached to a lower eyelid to measure an tear adsorbed distance on the strip to determine a quantity of tears Goren, M. B. et al: Am. J. Ophtalmol., 106, 570-4 (1988)!. According to the cotton thread test, a cotton thread stained with a pH indicator, etc. in advance is put in contact with tears in an eye and the discolored distance of the thread by tears adsorption is measured to determine an amount of tears Kunihashi, K. et al; Journal of Ped. Ophthalmol., 14, 390-7 (1977)!. The procedure of determination of tear evaporation includes a method of fixing humidity and temperature microsensors to a chamber, and putting the chamber over to measure a humidity increase within the chamber Tsubota, K. et al: Invest. Ophtalmol. Vis. sa: 33 (10) 2942-50 (1992)!.
Among the above-mentioned conventional test procedures for diagnosing dry eyes, the vital staining test is complicated in operation; the Shirmor's test gives rise to physical pains due to contact of a ship of filter paper with the lower eyelid; the cotton thread test is difficult in test manipulation due to the thinness of thread and consequent easy bending; and the conventional test procedure for quantitative determination of tear evaporation needs expensive apparatuses, etc.